Far Ultraviolet Spectroscopic Explorer Observations of the Supernova Remnant N49 in the Large Magellanic Cloud

We report a Far Ultraviolet Spectroscopic Explorer satellite observation of the supernova remnant N49 in the Large Magellanic Cloud, covering the 905-1187 Å spectral region. A 30'' square aperture was used, resulting in a velocity resolution of ~100 km s-1. The purpose of the observation was to examine several bright emission lines expected from earlier work and to demonstrate diffuse source sensitivity by searching for faint lines never seen previously in extragalactic supernova remnant UV spectra. Both goals were accomplished. Strong emission lines of O VI λλ1031.9, 1037.6 and C III λ977.0 were seen, Doppler broadened to ±225 km s-1 and with centroids redshifted to 350 km s-1, consistent with the LMC. Superposed on the emission lines are absorptions by C III and O VI λ1031.9 at +260 km s-1, which are attributed to warm and hot gas (respectively) in the LMC. The O VI λ1037.6 line is more severely affected by overlying interstellar and H2 absorption from both the LMC and our Galaxy. N III λ989.8 is not seen, but models indicate that overlying absorption severely attenuates this line. A number of faint lines from hot gas have also been detected, many of which have never been seen in an extragalactic supernova remnant spectrum.